What is Vitamin D?
Vitamin D isn’t just one thing. It’s actually a collection of molecules. Vitamin D made in our skin or absorbed from food starts off as inactive Vitamin D. It then travels to the liver where it is packaged into the circulating form of Vitamin D. This is what doctors measure when they order a Vitamin D blood test. Finally, the circulating Vitamin D is unpacked in the kidney to form Active Vitamin D, which is more than 100 times more potent than circulating Vitamin D.
The most well understood effect of Vitamin D is on the bones. It helps absorb minerals such as calcium, phosphorus and magnesium to help maintain strong bones. Vitamin D also helps the body breakdown old worn out bone and build new bone in its place. The major source of Vitamin D is direct sunlight. When sunlight reaches us on earth’s surface, it contains two types of UV light – UVA and UVB. UVB light from the sun interacts with a type of cholesterol in the skin to make Vitamin D. An important point here is that glass lets UVA pass through, but blocks UVB. This means that sunbaking behind your office window or in your car won’t help you make Vitamin D, but the UVA will still accelerate skin ageing and can increase the risk of skin cancer. Some foods do contain Vitamin D. The top 3 natural food sources are oily fish like salmon and tuna, beef liver and egg yolk. If your mum used to give you cod liver oil, it because it is the richest concentrated form of food Vitamin D.
What happens if I don’t get enough Vitamin D?
Have you heard of rickets? Well Vitamin D was originally discovered as a treatment for rickets. Rickets is a condition in children where bones are soft and weak. Children with rickets have deformed bones that can fracture easily. In adults, this condition of weak bones is called osteomalacia. Osteo means bone and malacia means soft. Many people with this condition have no symptoms at all. But if the bones continue to weaken over time, then people can develop deep and dull aching pain in their bones and even get fractures in unusual places like the ribs or spine.
People with Osteomalacia have very low Vitamin D levels in the body. There is a lot of buzz around the effects of Vitamin D and other aspects of our health like immune function, heart health and even cancer.
How much Vitamin D do I need?
Our skin is a Vitamin D making machine. There are two things that influence the amount of Vitamin D that our body is able to make: the first is our skin type and second is the amount of UV exposure. Exposure to UV light is a balancing act, too little and you risk becoming Vitamin D deficient, but too much increases your risk of skin cancer and accelerates skin ageing. It is really tricky to give specific recommendations on the amount of sunlight that each person needs and that’s because people’s skin types can vary so dramatically as can the amount UV in the environment. But overall you don’t need that much sunlight to get enough Vitamin D. Here is a quick formula that you can use as a guide. Just remember this guide is most applicable for people with fair skin which means Fitzpatrick skin types two to three. First, find out the maximum UV index in your city. The magic number is 3 – if the maximum UV index is less than 3, then about half an hour in the sun is recommended and you don’t need to use sun protection. If the maximum UV index is 3 or more, people with fair skin can produce enough Vitamin D very quickly. Just 5 to 10 minutes of sunlight is enough for adults, children and infants. There is a relatively high risk of getting sun burnt, so you should use sun protection if you plan to spend more than a few minutes outside.
Those guidelines are for people with fair skin. People with darker skin tend to be more UV resilient. Some studies suggest that Asian Indians need up to 3 times more sun, and those with African ancestry need up to 6 to 10 times more sun. Now some of you may not be able to get that much sunlight, either because of where you live, because of the type of job that you do, or certain health conditions. Assuming that you get practically no sunlight, then for adults, the recommended amount of Vitamin D from your diet is six hundred international units per day. That’s one hundred and twenty grams of salmon, one point three kilograms of beef liver, twenty-four thousand six hundred egg yolks, or just half a tablespoon of cod liver oil. Now if you’re not up to eating more than 24 thousand eggs or are vegetarian, then Vitamin D supplements may be worth your while. Vitamin D supplements can vary in their dose but the most common ones available from the pharmacy usually contain one thousand international units per capsule.
Can Vitamin D supplements cure cancer, prevent heart attacks and improve immunity?
The short answer, at this stage, is no. Vitamin D works by binding to a receptor called the Vitamin D receptor. This receptor sits on the nucleus of pretty much every body cell. So, in theory, Vitamin D can have lots of effects in the body. There have been many studies looking at the relationship between Vitamin D and other health conditions like cancer, heart disease and immune based conditions like asthma, but the results so far do not show convincingly show that giving Vitamin D reduces the risk of these conditions. Let us expalin that.. A study in 2012 combined the results of 19 different studies to see if Vitamin D levels are linked with heart disease. They found that as Vitamin D levels go up, the number of people with heart disease goes down. So more Vitamin D must protect against heart disease right? Building on this clue, researchers tested whether giving Vitamin D supplements can reduce the risk of heart diesease, but disappointingly there was no effect. The same thing happened with cancer – large population level studies found that there may be a link between Vitamin D and bowel cancer. But in trials where people were given Vitamin D supplements, there was no difference in cancer rates.
You might be thinking, well, why? Well one of the many reasons might be the age-old problem of correlation versus causation. When researchers do these big population level studies, they try to join the dots between two things to see if there is a link. Now even if we do find a link, we may miss some information in between. Going back to the example about heart disease, we found that more Vitamin D was linked with lower risk of heart disease. Well what do we know about Vitamin D? We know now that the major source for us is direct sunlight, and for people to get enough sun, they need to be fit enough to spend time outside. Is it possible that people who have enough Vitamin D, tend to be people who are fitter and healthier, and that’s why they don’t get heart disease? Vitamin D may be a marker of someone who is healthy and active, rather than something that prevents heart disease in itself. This is just one theory of what might be going on. There is a lot more research coming out and we are constantly learning new things. We know that having enough Vitamin D in the body is important for our health, especially for our bones. But any other health claim made about Vitamin D just doesn’t stack up yet.
Do I need to take a Vitamin D supplement?
For most healthy adults and children, sunlight in moderate amounts is all that’s needed to get enough Vitamin D. In fact the benefits of sunlight may extend beyond Vitamin D. It means that you are getting outside and getting some exercise and just being out in the sun may improve your mood. Another thing to remember that Vitamin D is one of the four fat soluble Vitamins, this means that the body can store Vitamin D and release it slowly. This means you don’t need sunlight everyday – the Vitamin D that your body makes and stores in the summer can be released slowly over a couple of months to get you through winter. There are definitely some people who are at high risk of Vitamin D deficiency and may benefit from taking Vitamin D supplements. This includes older people who are at risk of fractures, people who are naturally very dark skinned and live in less sunny climates, those who spend long hours indoors, and women that are already Vitamin D deficient and are planning a pregnancy.
If you think you or a family member are at risk of Vitamin D deficiency, have a chat to your doctor to see if a supplement may help you. One last thing, because Vitamin D is a fat soluble vitamin, your body can’t get rid of it if you take too much. Vitamin D from sunlight can never reach toxic levels, but Vitamin D from supplements can, especially if taken in very large doses. You should be especially careful with babies and children – they have small bodies and if they are given too much Vitamin D through supplements, it can quickly become toxic. There have been cases of children who suffered from a condition called hypercalcaemia because of excess Vitamin D given by their parents. Remember to talk to your paediatrician or GP before you give your children any kind of Vitamin D supplement.
The overall message for you is that Vitamin D is a balancing act – we know that too little is bad for you, but getting too much probably isn’t doing you any more good! It is about hitting that sweet spot to get the best of what Vitamin D can offer you.